Device and method for testing anchoring performance of grouting-free water-swelling anchor rod

Abstract

The invention discloses a grouting-free water-swelling anchor rod anchoring performance test device which comprises a reaction container, an elastic constraint assembly, a spiral anchor rod, a data acquisition assembly and an anchoring connection assembly. The reaction container is of a hollow cylinder structure with variable volume, and an openable cover plate is arranged at one end of the reaction container; the elastic constraint assembly is circumferentially arranged along the inner wall of the reaction container, and the rigidity of the elastic constraint assembly is adjustable to simulate different rock-soil body constraint conditions; the spiral anchor rod penetrates through the axial center of the reaction container and comprises a water injection channel and a stirring structure; the data acquisition assembly is arranged below the cover plate assembly and is used for monitoring reaction expansion force; the anchoring connection assemblies are arranged at the bottom of the reaction container and the top of the spiral anchor rod respectively and used for being connected with a testing machine for drawing testing. The rigidity-adjustable rubber spring inner wall and the variable container volume design are arranged for the water swelling material test, so that different environmental conditions are simulated, complex working conditions such as rock-soil cracks and crushing are dynamically reproduced, and the test result is close to a real anchoring scene.

Description

Technical Field

[0001] The invention belongs to the technical field of geotechnical anchorage tests, and particularly relates to a test device and a test method for the anchorage performance of a water-swelling bolt without grouting. Background Art

[0002] The anchorage support technology is a key technology used to enhance the stability of rock and soil masses in modern geotechnical engineering. This technology implants bolts in the rock and soil masses and uses the friction or adhesion between the bolts and the rock and soil masses to provide active support force and connect the unstable rock and soil masses with the stable rock and soil masses, thereby realizing the reinforcement of the rock and soil masses. Anchorage support includes various forms such as prestressed bolts, ordinary bolts, and anchor cables, and is widely used in projects such as tunnels, slopes, and foundation pits. It is an important means to ensure project safety and improve project stability.

[0003] In traditional anchorage grouting, due to the uncertainty of pressure grouting, the bolts cannot reach the designed support effect after installation, and more materials and equipment need to be invested, resulting in higher costs. In addition, traditional grouting materials are usually cement slurries. After hardening, the cement slurries may have air bubbles, forming voids, resulting in insufficient strength and poor adhesion. In low-temperature environments, they may also freeze, causing the components to crack, thus greatly reducing the effect of grouting reinforcement. Moreover, after the slurry is injected into the borehole, due to the too long reaction time, it will also cause a lag in the project cycle.

[0004] In current indoor pull-out tests, the grouting reaction device used is usually a rigid container. The volume of the container remains fixed during the reaction and curing process of the slurry. However, in actual anchorage projects, due to factors such as internal cracks and fractures in the rock and soil masses, the volume of the anchor solid is inconsistent with the designed volume, which has a certain impact on the performance of the bolts.

[0005] Nevertheless, the current research on bolt grouting materials still mainly focuses on enhancing cement grouting materials. There is no consideration of using water-swelling polymer materials for grouting tests, and the change in the volume of the test device during the reaction is rarely considered during indoor pull-out tests. There is a certain difference between the measured bolt pull-out resistance and the actual situation, which is not conducive to providing guidance for on-site construction. Summary of the Invention

[0006] The main purpose of the invention is to provide a test device and a test method for the anchorage performance of a water-swelling bolt without grouting for testing water-swelling materials.

[0007] The experimental device for the anchoring performance of the non-grouting water-swellable anchor provided by the present invention includes a reaction vessel, an elastic constraint assembly, a screw anchor, a data acquisition assembly, and an anchoring connection assembly; the reaction vessel is a hollow cylindrical structure with a variable volume, and one end thereof is provided with an openable cover plate; the elastic constraint assembly is arranged circumferentially along the inner wall of the reaction vessel, and its stiffness is adjustable to simulate different geotechnical constraint conditions; the screw anchor is arranged through the axial center of the reaction vessel and includes a water injection channel and a stirring structure; the data acquisition assembly is arranged below the cover plate assembly for monitoring the reaction expansion force; the anchoring connection assembly is respectively arranged at the bottom of the reaction vessel and the top of the screw anchor for connecting a testing machine for pulling test.

[0008] In an embodiment of the above device, the elastic constraint assembly is a rubber spring formed by 3D printing, which has a hollow cylindrical structure with a preset stiffness and is fixed to the inner wall of the reaction vessel by an adhesive method.

[0009] In an embodiment of the above device, the screw anchor assembly includes a hollow steel pipe body, spiral steel sheets welded to the lower end, a plurality of water outlets arranged on the side wall, and a sealing ring sleeved on the middle section of the steel pipe, and the outer diameter of the sealing ring is larger than the opening of the cover plate to form a sealing structure.

[0010] In an embodiment of the above device, the cover plate includes a steel cover plate, a feed port arranged through, an exhaust channel with a valve, and a pressure sensor integrated on the lower surface of the cover plate, and the cover plate is detachably connected to the reaction vessel through a flange connection structure.

[0011] In an embodiment of the above device, the pressure sensor is a disc-shaped miniature earth pressure sensor, and its data line is led out through a through hole in the groove on the lower surface of the cover plate.

[0012] In an embodiment of the above device, the anchoring connection assembly includes a threaded bottom rod welded to the bottom of the reaction vessel and an anchor clamp arranged on the top of the screw anchor.

[0013] In an embodiment of the above device, the anchor clamp includes a nut, a square connecting piece, and a hollow steel pipe welded and fixed in sequence from top to bottom; the nut is threadedly connected to the upper end of the screw anchor, and fixing holes are provided on the hollow steel pipe.

[0014] In an embodiment of the above device, the reaction vessel is a cylindrical structure made of a transparent material, and a flange plate with bolt holes is provided at the open end, and the threaded bottom rod is welded to the center of the closed end.

[0015] A method for conducting an experiment using the above device is as follows:

[0016] 1. Assemble the instrument

[0017] Assemble the reaction vessel, rubber spring, screw anchor bolt and cover plate in sequence according to requirements, and connect the pressure sensor with the acquisition instrument;

[0018] 2. Injection and reaction

[0019] Prepare the corresponding reaction liquid according to the design requirements and place it in the container in advance. Then inject water into the container through the anchor bolt. When it is observed that the reaction liquid will overflow from the feed port, quickly close the feed port and the exhaust valve, and let it stand for reaction;

[0020] 3. Dismantle the cover plate

[0021] After reaching the designed reaction time, turn off the pressure sensor, record the data of the change in expansion force during the reaction process, remove the bolts on the cover plate, and dismantle the cover plate;

[0022] 4. Pull-out test

[0023] Connect and fix the reaction vessel with the testing machine, and conduct the pull-out test according to requirements. Record the changes in pull-out displacement and pull-out force during the test process;

[0024] 5. Clean the device

[0025] After the pull-out test is completed, remove the residues on the surface of the anchor bolt, inside the reaction vessel and on both sides of the cover plate to facilitate the next use;

[0026] 6. Control test

[0027] Refer to the above steps to prepare slurries with different qualities and ratios, repeat the pull-out test, and study the relationship between the slurry quality and ratio and the pull-out resistance and pull-out displacement;

[0028] 7. Comparative analysis

[0029] Compare and analyze the differences in the pull-out force - pull-out displacement curves of different slurry qualities and ratios, conduct a theoretical analysis on the pull-out performance of the anchor bolt under different slurry ratios, analyze the ultimate pull-out force and pull-out displacement of the anchor bolt when injecting different slurry qualities and ratios, and obtain the optimal slurry quality and ratio of the anchor bolt.

[0030] The beneficial effects of the present invention are as follows:

[0031] 1. For the test of water-swellable materials, an inner wall of a rubber spring with adjustable stiffness and a variable container volume design are set up to simulate different environmental conditions, dynamically reproduce complex working conditions such as rock and soil fractures and breakages, and make the indoor test results closer to the real anchoring scenario;

[0032] 2. The screw anchor bolt is provided with a water outlet and spiral steel sheets. The water outlet is used for water injection to achieve the function of avoiding grouting. The spiral steel sheets rotate during use to fully mix water and slurry, increasing the test efficiency;

[0033] 3. By comparing and analyzing slurries with different reactant masses or different reactant ratios, evaluate the reactant mass and ratio of this grout-free expanding anchor bolt; at the same time, conduct a pull-out performance evaluation, and determine the optimal mass and ratio through the change of the reactant mass / ratio - pull-out force curve to provide reference for on-site construction. Description of the Drawings

[0034] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present invention.

[0035] Figure 2 is Figure 1 a schematic diagram of the structure of the reaction vessel in

[0036] Figure 3 is Figure 1 a schematic diagram of the structure of the cover plate in

[0037] Figure 4 is Figure 1 a schematic diagram of the structure of the screw anchor in

[0038] Figure 5 is Figure 1 a schematic diagram of the structure of the anchor bolt clamp in

[0039] Reference Numerals:

[0040] 1. Reaction vessel; 2. Cover plate; 3. Rubber spring; 4. Screw anchor; 5. Anchor bolt clamp; 6. Flange; 7. Threaded bottom rod; 8. Flange opening; 9. Feed port; 10. Exhaust valve; 11. Pressure sensor; 12. Cover plate opening; 13. Cover plate opening; 14. Screw steel sheet; 15. Sealing ring; 16. Water outlet; 17. Nut; 18. Square connecting piece; 19. Fixing hole. Detailed Embodiments

[0041] Next, the related technical solutions will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0042] As Figure 1 shown, this grout-free water-swellable anchor bolt anchoring performance test device disclosed in this embodiment includes a reaction vessel 1, a cover plate 2, a rubber spring 3, a screw anchor 4, and an anchor bolt clamp 5.

[0043] As Figure 2As shown, the reaction vessel 1 is a transparent hollow cylindrical structure, open at one end and closed at the other. A flange 6 is welded to the open end, and 4 bolt holes 8 are evenly distributed around the flange; a threaded bottom rod 7 is welded to the center of the closed end for fixing to the testing machine.

[0044] Inside the inner wall of the reaction vessel 1, a rubber spring 3 is adhered by glue. The rubber spring is a hollow cylindrical spring made of 3D printed elastic material, with a preset stiffness and friction coefficient; its hollow cylindrical structure fits tightly against the inner wall of the reaction vessel 1, providing adjustable constraint conditions to simulate the fracture environment of rock and soil masses.

[0045] The rubber spring 3 has a certain thickness, and at the same time, there is enough space inside the reaction vessel 1 to place the screw anchor 4.

[0046] As Figure 3 shown, the cover plate 2 is a steel solid disk, with an outer diameter the same as that of the flange 6, and 4 bolt holes 12 are correspondingly set around it, and it is connected to the reaction vessel 1 by bolts. An anchor hole 13 is provided in the center of the cover plate, and the hole diameter allows the screw anchor 4 to pass through.

[0047] On the upper surface of the cover plate 2, a through feed port 9 and an exhaust valve 10 with a switch valve are provided; on the lower surface, a circular groove is opened, a through hole is provided in the middle of the groove, and a disk-shaped micro earth pressure sensor 11 is placed inside, and the sensor data line is led out through the hole to the outside.

[0048] As Figure 4 shown, the screw anchor 4 includes a hollow steel pipe, a spiral steel sheet 14 and a sealing ring 15.

[0049] Threads are processed on the upper section surface of the hollow steel pipe, and the spiral steel sheet 14 is welded to the lower end, and the two are connected by the sealing ring 15; the sealing ring is a solid ring with an outer diameter slightly larger than the diameter of the hollow steel pipe, used to seal the anchor hole 13 of the cover plate 2 to ensure airtightness. A plurality of water outlets 16 are opened on the side wall of the lower end of the anchor for injecting water to mix with the slurry.

[0050] The screw anchor 4 is placed inside the reaction vessel 1, and the spiral steel sheet 14 at the lower end of the anchor is located in the hollow area of the vessel.

[0051] As Figure 5 shown, the anchor clamp 5 includes a nut 17, a square connecting piece 18 and a hollow steel pipe welded and fixed in sequence from top to bottom. The nut is threadedly connected to the upper end of the screw anchor 4, and a fixing hole 19 is opened on the hollow steel pipe, and it is fixed to the testing machine joint by a pin to realize the transfer of the pulling force.

[0052] This test device can be used for indoor anchoring tests. By configuring reaction liquids of different types (such as slurry types, ratios, etc.) and injecting them into the container through the feed inlet, a closed reaction can be achieved within the container to simulate different slurry working conditions in engineering. Different internal structures of the container (such as stiffness, roughness, etc.) can be set according to requirements to simulate different environmental conditions in actual engineering;

[0053] At the same time, this test device can continuously record the data of the change in swelling force during the reaction process. Through the pressure sensors and their acquisition instruments set in this device, the change data of the swelling force with the reaction time can be obtained, so as to analyze the swelling performance of different slurries.

[0054] The method of using this test device for testing is as follows:

[0055] 1. Assemble the instrument

[0056] Assemble the reaction container 1, rubber spring 3, screw anchor 4 and cover plate 2 in sequence. The anchor clamp 5 is installed during the pull-out test. The rubber spring 3 is placed on the inner wall of the reaction container and bonded with a specific glue. The anchor 4 is placed into the reaction container. The cover plate 2 passes through the anchor along the middle opening, and then the cover plate and the reaction container are fixed with bolts and nuts. When fixing, it is necessary to ensure that the tightening degree of the bolts is the same to ensure airtightness;

[0057] 2. Inject materials and react

[0058] Configure the corresponding masses of polyurethane slurry and water according to the design requirements. First, place the polyurethane slurry into the container along the feed inlet 9 on the cover plate, and pay attention to preventing the slurry from overflowing during injection. Then, inject water along the anchor feed inlet to avoid grouting during the test. After the water injection is completed, rotate the part of the anchor outside the cover plate to make the polyurethane slurry and water fully stirred in the container through the spiral steel sheet. After the stirring is completed, fix the anchor 4 and the cover plate 2 with nuts. When observing that a small amount of slurry is about to overflow from the feed inlet, quickly close the feed inlet and the exhaust valve, and let the container stand for reaction;

[0059] 3. Dismantle the cover plate

[0060] After reaching the designed reaction time, first record the change data of the swelling force during the reaction recorded by the acquisition instrument, then turn off the pressure sensor, and then remove the bolts and nuts on the cover plate 2 one by one, and then remove the cover plate 2 along the outer end of the anchor 4;

[0061] 4. Pull-out test

[0062] The pull-out test shall use a testing machine that meets the requirements. First, fix the container to the upper end of the testing machine through the threaded bottom rod 7 at the lower end. At this time, the container is hanging upside down on the testing machine. Then, install the anchor rod clamp 5 to the outer end of the anchor rod, pass a pin through the fixture fixing hole 19 and the lower end joint of the testing machine, and then conduct the pull-out test as required until the anchor rod 4 is pulled out from the container. During the test, record the change data of the pull-out force and the pull-out displacement through the acquisition device of the testing machine;

[0063] 5. Cleaning device

[0064] After the pull-out test is completed, remove the residues on the surface of the anchor rod 4, inside the reaction container 1, and on both sides of the cover plate 2, and dredge the feed inlet 9 and the exhaust valve 10 for the next use;

[0065] 6. Control test

[0066] Refer to the above steps to prepare reaction liquids with different masses and ratios, repeat the pull-out test, and study the relationship between the density and ratio of the reactants and the ultimate pull-out force and the pull-out displacement;

[0067] 7. Comparative analysis

[0068] Compare and analyze the differences in the pull-out force - pull-out displacement curves of different slurry masses and ratios, conduct a theoretical analysis of the pull-out performance of the anchor rod under different slurry ratios, analyze the ultimate pull-out force and the pull-out displacement of the anchor rod when injecting different slurry masses and ratios, and obtain the optimal slurry mass and ratio of the anchor rod.

[0069] In the injection reaction step of the above method, a single-component oil-soluble polyurethane material is used as the grouting material, which has the characteristics of water swelling, good adhesion, and excellent mechanical properties after consolidation.

[0070] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the above embodiments have been described in detail, those skilled in the art can still modify the technical solutions recorded in the above embodiments or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An experimental device for the anchoring performance of a water-swelling bolt without grouting, characterized in that: It includes a reaction vessel, an elastic constraint component, a screw anchor, a data acquisition component and an anchoring connection component; The reaction vessel is a hollow cylindrical structure with a variable volume, and one end thereof is provided with an openable cover plate; The elastic constraint component is arranged circumferentially along the inner wall of the reaction vessel, and its stiffness is adjustable to simulate different geotechnical constraint conditions; The screw anchor is arranged through the axial center of the reaction vessel and includes a water injection channel and a stirring structure; The data acquisition component is arranged below the cover plate assembly for monitoring the reaction expansion force; The anchoring connection components are respectively arranged at the bottom of the reaction vessel and the top of the screw anchor for connecting the testing machine to conduct a pull-out test.

2. The water-injection-free water-swellable anchor bolt anchoring performance test device according to claim 1, characterized in that: The elastic constraint component is a rubber spring formed by 3D printing, which has a hollow cylindrical structure with a preset stiffness and is fixed to the inner wall of the reaction vessel by an adhesive method.

3. The water-injection-free water-swellable anchor bolt anchoring performance test device according to claim 1, characterized in that: The screw anchor component includes a hollow steel pipe body, spiral steel sheets welded to the lower end, a plurality of water outlets arranged on the side wall, and a sealing ring sleeved on the middle section of the steel pipe. The outer diameter of the sealing ring is larger than the opening of the cover plate to form a sealing structure.

4. The water-injection-free water-swellable anchor bolt anchoring performance test device according to claim 1, characterized in that: The cover plate includes a steel cover plate, a feed port arranged therethrough, an exhaust channel with a valve, and a pressure sensor integrated on the lower surface of the cover plate. The cover plate is detachably connected to the reaction vessel through a flange connection structure.

5. The water-injection-free water-swellable anchor bolt anchoring performance test device according to claim 4, wherein: The pressure sensor is a disc-shaped micro earth pressure sensor, and its data line is led out through a through hole in the groove on the lower surface of the cover plate.

6. The water-injection-free water-swellable anchor bolt anchoring performance test device according to claim 1, characterized in that: The anchoring connection component includes a threaded bottom rod welded to the bottom of the reaction vessel and an anchor clamp arranged at the top of the screw anchor.

7. The water-injection-free water-swellable anchor bolt anchoring performance test device according to claim 6, wherein: The anchor clamp includes a nut, a square connecting piece and a hollow steel pipe welded and fixed in sequence from top to bottom; the nut is threadedly connected to the upper end of the screw anchor, and fixing holes are provided on the hollow steel pipe.

8. The anchoring performance test device for water-swelling bolt without grouting according to claim 6, characterized in that: The reaction vessel is a cylindrical structure made of a transparent material, and a flange plate with bolt holes is provided at the open end, and the threaded bottom rod is welded to the center of the closed end.

9. A method for conducting an experiment by using the experimental device for testing the anchoring performance of a water-swelling bolt without grouting according to any one of claims 1-8, and the specific steps are as follows:

1. Assemble the instrument Assemble the reaction vessel, rubber spring, screw anchor and cover plate in sequence according to the requirements, and connect the pressure sensor with the acquisition instrument; 2. Inject materials and react Prepare the corresponding reaction liquid according to the design requirements and place it in the container in advance, and then inject water into the container through the anchor. When it is observed that the reaction liquid will overflow from the feed port, quickly close the feed port and the exhaust valve, and let it stand for reaction; 3. Disassemble the cover plate After reaching the designed reaction time, turn off the pressure sensor, record the change data of the expansion force during the reaction process, take out the bolts on the cover plate, and remove the cover plate; 4. Pull-out test Connect and fix the reaction vessel with the testing machine, conduct a pull-out test according to the requirements, and record the changes of the pull-out displacement and the pull-out force during the test process; 5. Clean the device After the pull-out test is completed, remove the residues on the surface of the anchor, inside the reaction vessel and on both sides of the cover plate to facilitate the next use; 6. Control experiment Prepare slurries with different qualities and ratios with reference to the above steps, repeat the pull-out test, and study the relationship between the slurry quality and ratio and the pull-out resistance and the pull-out displacement; 7. Comparative analysis Compare and analyze the differences in the pull-out force-pull-out displacement curves of different slurry qualities and ratios, conduct a theoretical analysis of the anti-pulling performance of anchor bolts under different slurry ratios, analyze the ultimate pull-out force and pull-out displacement of anchor bolts when injecting different slurry qualities and ratios, and obtain the optimal slurry quality and ratio of anchor bolts.

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